Crews respond to a fire on May 14 at Camp Pendleton in California. / U.S. Marine Corps

by William M. Welch and John Bacon, USA TODAY

by William M. Welch and John Bacon, USA TODAY

Brush fires fanned by hot, dry winds ignited across Southern California on Wednesday, prompting thousands of people to flee homes, schools and businesses.

At least eight serious brush fires were ignited in San Diego County, with more in Los Angeles and surrounding areas.

Schools across San Diego canceled Thursday classes, and a university campus, California State-San Marcos, was evacuated. Its weekend graduation ceremonies were canceled.

Gov. Jerry Brown declared a state of emergency for San Diego County, which would free up special resources and funding for the firefight, and state fire officials were creating a central command center for the blazes.

Fire officials said a fast-growing fire at Carlsbad north of San Diego consumed 400 acres and was only 10% contained by evening. Carlsbad officials said more than 23,000 notifications of evacuations - some mandatory, some voluntary - were sent to residents, businesses and cellphones in the area.

Capt. Mike Mohler, of the state firefighting agency CalFire, told KCAL-TV as many as 30 structures had burned. Carlsbad officials later reported 16 homes, eight of them apartments in one building, were among them.

The fires were whipped by a Santa Ana wind system that reverses the normal flow of wind from the Pacific Ocean and creates tinderbox fire conditions.

The rash of fires and extreme conditions was unusual for this time of year. Southern California's fire season usually begins in late summer and fall, but the entire state has been gripped by prolonged drought, leaving vast areas of underbrush dry and ready to burn.

Temperatures soared to 100 degrees or more. Firefighters said winds, with gusts of up to 50 mph, sent embers flying a half mile ahead, igniting more brush and structures.

KCAL-TV aired helicopter footage of one fire burning unchecked alongside Interstate 405 near the intersection with state Highway 118 in the San Fernando Valley of Los Angeles. The fire sent flames and towers of black smoke across the freeway as cars continued to pass by before the arrival of firefighters. The fire was contained, but evening commuters faced long backups.

To the south in San Diego County, the Legoland California amusement park was evacuated after fire knocked out power lines, resort spokeswoman Julie Estrada said.

The Carlsbad fire spread to homes after starting shortly before 11 a.m. and grew rapidly, Winds were 25 mph, the temperature was 100 degrees and relative humidity only 3%, extremely low, according to the National Weather Service.

Mohler said Legoland was not under immediate threat but is near the fire area. Two elementary schools and a middle school were evacuated.

TV news video from the Carlsbad area fire showed homes engulfed in flames and other neighbors struggling to protect their property.

Fires at Camp Pendleton, the large Marine Corps base on the coast in northern San Diego County, prompted evacuation of some base housing. Some 6,000 acres were reported burned.

A red flag warning indicating extreme fire conditions was scheduled to be lifted at 8 p.m. for some areas but was extended through most of Thursday for Los Angeles.

The weather was forecast to remain hot, following a record-setting scorcher Wednesday. Temperatures topped 100 degrees from north of Los Angeles to San Diego at the border with Mexico. Even beach areas normally cooled by the Pacific breezes saw high temperatures: 101 at Long Beach and 99 at Laguna Beach.

An afternoon brush fire at an exit ramp prompted the closing in both directions of the 91 Freeway through Anaheim. The fire was contained and the freeway reopened.

A fire that broke out Tuesday in San Diego was 25% contained Wednesday after consuming 1,548 acres, said Daniel Berlant, spokesman for CalFire, also known as the California Department of Forestry and Fire Protection. Another fire that started Tuesday in Santa Barbara County was 50% contained after burning 600 acres, CalFire reported.

At Camp Pendleton, home to about 42,000 military personnel, employees of a naval weapons station, residents of base housing development and an elementary school were told to evacuate. Marine Sgt. Irons told USA TODAY the Pendleton evacuation effort included residents of DeLuz base housing, personnel at Naval Weapons Station Fallbrook and students and staff at Mary Fay Pendleton Elementary School.